JP2006248714A - Sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder having a large capacity as a simple universal style, and capable of handling sheets having various kinds of sizes, and of feeding sheets without trouble. <P>SOLUTION: This automatic sheet feeder is provided with: an intermediate plate for stacking a plurality of sheets thereon; an intermediate plate pressing spring for pushing up the intermediate plate to bring the uppermost sheet out of the stacked sheets into contact with a sheet feed means; two sheet size restriction plates movably arranged for restricting end faces parallel with the sheet feed direction of the sheets having different sizes; a weight (balancer) mounted movably to the intermediate plate. The sheet feeder is characterized by that the fixation of the weight is changed over to the movement thereof in conjunction with the sheet size restriction plate and the weight is moved in conjunction with the angle of the intermediate plate in a moving mode, whereby force for pressing the uppermost sheet against a paper feed roller is kept in a certain range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet feeding device that sequentially feeds sheets to an image forming unit such as a copying machine, a laser printer, and a facsimile machine.

  Conventionally, as an automatic paper feeder for a copying machine or a printer, the simple type shown in FIG. 9 has been used. In this automatic paper feeder, a stacking plate 2 is installed on the bottom of the cassette 1 so as to be swingable up and down with a support shaft 3 as a fulcrum, and the leading end of the stacking plate 2 is pushed up by a coil spring 5 to feed paper P. The roller 9 is configured to be in pressure contact. In FIG. 9, reference numeral 6 denotes a rear end restricting plate, and reference numeral 7 denotes a side restricting plate. Both restricting positions are variable according to the sheet size.

By the way, the automatic paper feeder is a universal system, and various sizes of paper are loaded. Although the paper feeding pressure is applied by the spring 5, if the paper is different in size, the weight is different even if the number of sheets is the same. Specifically, the sheet feeding force F1 is determined by the equation (1) from the pressing force F2 against the sheet feeding roller 9 by the spring 5 and the friction coefficient μ of the sheet feeding roller 9. Further, the pressing force F2 is a force Fsp of the spring 5 and a paper weight component Fp acting on the spring 5.
Is determined by equation (2).

F1 = F2 × μ (1)
F2 = Fsp−Fp (2)
As is clear from the above equation (1), the sheet feeding force F1 is a function of the pressing force F2, and as shown in FIG. 10, when the pressing force F2 is small (see the area A with hatching in FIG. 10). ), The paper feeding force F1 is also reduced, and non-feed (no paper feeding) occurs. On the other hand, when the pressing force F2 is large (see the hatched area B in FIG. 10), “double feeding” in which two or three sheets are fed simultaneously occurs.

  Here, considering the relationship between the paper size and the pressing force F, as shown in FIG. 11, since the paper weight component Fp is small at the minimum size, the pressing force F2 becomes relatively large and the double feed area. Overlap B. On the other hand, since the paper weight component Fp is large at the maximum size, the pressing force F2 becomes relatively small and overlaps with the paper feeding error area A.

  Therefore, in the case of a large-capacity cassette that can handle a small size to a large size, the slope of the graph in FIG. 11 is changed between the small size and the large size, and the shaded area (the unfeedable A area and the double feed area in the figure). B) is avoided.

  As means for changing the inclination, a plurality of springs are arranged to selectively act on a plurality of springs according to the paper size (see, for example, Patent Document 1), or the height of the spring receiving surface is made movable to make the paper size. A method of changing the pressing force F2 by the spring according to the above (for example, see Patent Document 2) has been proposed.

JP-A-11-116073 Japanese Patent Laid-Open No. 61-022647

  However, in the system in which the plurality of springs are provided and selectively actuated, when the height of the apparatus is increased by adding a spring pressing member used when one of the springs is not operated, or when interlocked with the paper trailing edge regulating plate, A5 Since the rear end regulating plate position is the same as that in the A4 horizontal feed, the pushing force F increases and enters the multifeed area B, and does not hold. There is a problem that it ends up.

  In addition, the height of the spring receiving surface can be moved by increasing the height of the device, deteriorating operability when the receiving surface is moved to the user, and an interlocking mechanism when interlocking with the paper regulating plate. There are problems such as complexity.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a paper feeding device that can handle various sizes of paper with a large capacity as a simple universal system and can feed paper without any trouble. To do.

  In order to achieve the above object, an automatic paper feeder according to the present invention applies an intermediate plate on which a plurality of papers are stacked and an uppermost paper that is stacked by pushing up the intermediate plate to the paper supply means. Middle plate pressure spring to be contacted, two paper size regulation plates movably arranged to regulate the end face parallel to the feeding direction of different size paper, and movable relative to the middle plate The weight (balancer) is attached to the paper size, and the weight is fixed and moved in conjunction with the paper size restriction plate, and the weight moves in conjunction with the angle of the middle plate in the movement mode. The pressing force of the paper to the paper feed roller is maintained within a certain range.

  According to the present invention, in order to keep the paper feeding pressure within a certain range by changing the acting force of the weight on the paper feeding pressure, the change in the working force due to the weight movement is activated when feeding small size paper. This eliminates the phenomenon of excessively high feeding pressure when loading small-size paper, and achieves the same size as the conventional cassette without using a complicated mechanism. It is possible to realize a 500-sheet feeding cassette that can provide high reliability and stable sheet feeding performance while maintaining.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
Hereinafter, the sheet feeding operation from the sheet feeding apparatus to the image forming apparatus main body (not shown), the sheet conveyance sequence, and the like are the same as those in the related art, and are omitted.

  1 and 2 are a top view and a main cross-sectional view in the side direction of the sheet cassette unit according to the present embodiment.

  In the figure, reference numeral 100 denotes a paper feed cassette, which can accommodate 500 sheets. When desired sheets are stored in the sheet feeding cassette 100 and mounted on the image forming apparatus main body (not shown), one sheet at a time from the uppermost sheet P by a sheet feeding roller (not shown) disposed above the sheet feeding cassette 100. Paper can be fed.

  Next, the configuration of the paper feed cassette 100 will be described in detail.

  Reference numeral 11 denotes a cassette body, which is coupled to or integrally formed with the cassette front cover, and has rail surfaces 11a and 11b on the left and right sides. The handle 12 of the sheet feeding cassette 100 is engaged with rails provided in the image forming apparatus. Thus, the drawer operation is made to function. The paper accommodating portion of the cassette body 11 has side restricting plates 13 and 14 for restricting the side edges of the paper to be accommodated and a rear end restricting plate 15 for restricting the rear end of the paper.

  The side regulating plates 13, 14 are provided with a rack portion that meshes with the pinion gear 16 in order to move integrally according to the paper width to be accommodated. The rear end regulating plate 15 is slidably disposed on the cassette body 11 so as to be able to move in accordance with the rear end of the paper. Reference numeral 17 denotes a paper stacking plate (hereinafter referred to as “middle plate”), which is supported rotatably about bosses 22 and 23 provided at both ends. An intermediate plate spring 18 as a push-up member is provided on the lower surface of the intermediate plate 17 and urges the intermediate plate 17 upward to generate a paper supply pressure between the uppermost paper and the paper supply roller. is there.

  Next, the intermediate plate pressurizing structure, which is a feature of the present invention, will be described in detail with reference to FIGS.

  Balancers (weights) 24 and 25 are arranged on the intermediate plate 17 in order to adjust the sheet feeding pressure. The balancers 24, 25 are provided with tension springs 26, 27, and the balancers 24, 25 receive a tensile force in the conveying direction in the figure by the action of the tension springs 26, 27. The side regulating plates 13 and 14 are provided with lock ribs 13a and 14a for regulating the movement of the balancers 24 and 25, respectively.

  Hereinafter, the positions of the balancers 24 and 25 that vary depending on the size and number of sheets placed on the intermediate plate 17 will be described.

  The side regulating plates 13 and 14 in FIG. 1 indicate the position at the A3 size, which is the maximum sheet size that can be loaded. At this time, the balancers 24 and 25 are regulated by the lock walls 13a and 14a. It is in the position shown in FIG. FIGS. 3A and 3B are side views when the paper size is A3 full load and when the last paper (one sheet is loaded). At this time, the balancers 24 and 25 are the lock walls 13a and 14a as described above. Is fixed at the position (first position) in the figure.

  Next, FIG. 4 and FIG. 5 show a top view and a side view of the state when the B5R size, which is the minimum size that can be accommodated in the paper feed cassette 100 according to this embodiment, is set.

  As shown in FIG. 5, since the side regulating plates 13 and 14 move toward the center during B5R, the balancers 24 and 25 are unlocked.

  When the B5R size paper is fully loaded, the intermediate plate angle θ is almost 0 degrees as shown in FIG. 5B. Therefore, the balancers 24 and 25 are moved to the right in FIG. Balance at 5 (b). The balance between the spring pressure and the balancer at this time is expressed by the following equation.

μM = kL1 (1)
Where μ is the coefficient of static friction between the intermediate plate and the balancer, M is the balancer weight, k is the spring constant of the tension spring, and L1 is the tension spring length in the state of FIG.

  Next, B5R size paper will be described with reference to FIG.

  As shown in the figure, in the last paper feeding state, the balancers 24 and 25 are balanced at the positions in the figure, and these positions are set to be the same as the positions when the A3 is loaded. The balance between the spring pressure and the balancer at this time is expressed by the following equation.

Msin θ = k (L2−L1) (2)
Here, θ is the intermediate plate angle, L2 is the tension spring length in the state shown in FIG. 5A, and the balancers 24 and 25 are set when the small-size paper is released so that the lock walls 13a and 14b are released. As the intermediate plate angle θ increases, the position smoothly moves from the position shown in FIG. 5B to the position shown in FIG.

  When the distance from the center rotation center of the middle plate to the balancers 24 and 25 at full load is r and the distance to the nip between the paper feed roller and the uppermost paper is r1, the acting force F of the balancers 24 and 25 on the paper feed pressure F Is expressed by the following equation.

F = r / r1 · M cos θ (3)
Accordingly, the paper feed pressure Q is obtained from the following equation.

Q = P-W-F (4)
Here, P: acting force by the middle plate spring 18; load on the middle plate (the sum of the weight of the middle plate excluding the balancer and the sum of the weights of the stacked sheets).

  FIG. 6 shows the transition of the paper feed pressure setting from full load to last paper in A3 size in the present embodiment.

  As described above, since the balancers 24 and 25 are fixed in the A3 size paper, the acting force of the balancer is represented by a gentle curve with a downward slope to the right.

  FIG. 7 shows the transition of the paper feed pressure setting from full load to last paper in the B5R size in this embodiment.

  As described above, in the B5R size paper, the balancers 24, 25 continuously move from the second position when fully loaded to the first position of the last paper according to the angle θ of the intermediate plate 18, so the acting force of the balancer is It is represented by a downward-sloping curve, and the inclination is larger than in the case of the A3 size paper. By providing a difference in balance force between the full load and the last paper, the appropriate paper feed pressure is satisfied in all sizes A3 to B5R.

  Therefore, although not shown, it is needless to say that the proper paper feeding pressure is satisfied even in other paper sizes that can be accommodated, such as B4 and A4.

  As described above, 500 sheets can be supplied without having to use a complicated mechanism and without increasing the size of the paper feed cassette, and can maintain stable paper feed pressure from a large size to a small size and provide stable paper feed performance. Realized paper cassette.

<Embodiment 2>
FIG. 8 is a main cross-sectional view of the second embodiment.

  Since the present embodiment is different from the first embodiment only in the balancer configuration and the spring constant of the tension spring, description of other parts is omitted.

  The balancer is composed of a main body portion 32 which is a connecting portion with the tension spring 33, a rotatable roller portion 31, and a roller portion 31 and a bearing portion 33 which is provided in the main body portion 32 and can rotate the roller portion with almost no resistance. Has been. In the balancer configuration according to the present embodiment, the friction coefficient between the sheet feeding roller portion 31 of the balancer and the intermediate plate 17 is significantly smaller than that of the first embodiment due to the effect of the bearing portion 33.

  Therefore, the spring constant k of the tension spring 33 according to the equation (1) described in the first embodiment can be reduced, and the spring pressure of the tension spring 33 can be set weak. Thereby, it is possible to increase the amount of movement of the balancer from the time of full load to the time of last from the equation (2). In addition, this makes it easy to keep the paper feed pressure Q within a certain range, and the degree of freedom of design for realizing the present invention is widened.

It is a top view of the paper feed cassette according to Embodiment 1 of the present invention. It is a main sectional view of a paper feed cassette concerning Embodiment 1 of the present invention. It is a main sectional view showing the A3 size paper used in the paper feed cassette according to the first embodiment of the invention. It is a top view which shows the time of B5R paper use of the paper feed cassette which concerns on Embodiment 1 of invention. It is a main sectional view showing the B5R paper at the time of use of the paper feed cassette concerning Embodiment 1 of the invention. It is a graph which shows the paper feed pressure at the time of A3 size paper use of the paper feed cassette which concerns on Embodiment 1 of invention. 6 is a graph showing a sheet feeding pressure when using a B5R size sheet of the sheet feeding cassette according to the first embodiment of the invention. It is a main sectional view showing a paper feed cassette concerning Embodiment 2 of the invention. It is sectional drawing which shows the conventional automatic paper feeder. It is a graph which shows the paper feed pressure in the conventional automatic paper feeder. It is a graph which shows the relationship between the paper size and pressing force in the conventional automatic paper feeder.

Explanation of symbols

11 Middle plate 13, 14 Side regulating plate 13a, 14b Lock wall 18 Middle plate spring 24, 25 Balancer (weight)
26, 27 Tension spring

Claims (5)

  Paper feeding rollers that feed paper, a middle plate on which a plurality of papers are stacked, a spring that pushes up the middle plate and abuts the topmost paper loaded on the paper, and different sizes In order to regulate the end face parallel to the paper feeding direction of the paper, there are provided two paper size regulating plates movably arranged, and load means that acts on the middle plate in the direction opposite to the spring. The function of the load means is increased / decreased depending on the paper size loaded on the middle plate, and the load means is most effective when the minimum size paper that can be loaded and fed on the middle plate is full. Characteristic paper feeder.   The load means is interlocked with the position of the paper side restriction plate. When the distance L between the paper side restriction plates is L: M with the distance M as a boundary, the load means is fixed to the middle plate. The action on the intermediate plate is constant, and when L <M, the load means is movable with respect to the intermediate plate and moves in conjunction with the change in the angle of the intermediate plate. The paper feeder described.   The sheet feeding device according to claim 2, wherein the distance M is in a range of 182 mm to 257 mm.   2. The load means includes a spherical weight, an elastic member that couples the weight and an intermediate plate, and a weight regulating member that operates in conjunction with the movement of the paper side regulating plate. The sheet feeding device according to any one of?   The load means includes a tire-shaped weight, an elastic member that couples the weight and the middle plate, and a weight regulating member that operates in conjunction with the movement of the paper side regulating plate. The main body unit for coupling the elastic member, a roller unit rotatably contacting the surface of the intermediate plate, and a bearing unit provided between the main body unit and the roller. The paper feeder described in 1.

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